In the field of wireless communication systems, resource allocation and resource sharing represent important issues. This is particularly due to the fact that a band (i.e. frequency spectrum), on which resources are available for a specific communication or system, and thus the resources are limited.
In the field of wireless communication systems, it may be differentiated between cellular communication networks typically utilizing scheduling-based channel access mechanisms on a licensed spectrum, and local area networks typically utilizing non-scheduled (contention-based) channel access mechanisms on an unlicensed spectrum.
In recent years, cooperation and interworking (also referred to as merging) of different types of networks and systems has received increasing attention. In this regard, efforts are made for realizing a combination of cellular communication networks and local area networks. Such combined system may for example be usable for accomplishing cellular offloading, wherein traffic is offloaded from a cellular communication network to a local area network (such as WLAN) so as to reduce the load on the cellular communication network, and network-controlled device-to-device (D2D) communication, wherein devices such as user equipments (UE) or terminals directly communicate with each other without involving a network entity such as a base station or access node of a cellular communication network. Insofar, a D2D communication may also serve for cellular offloading purpose (in addition to an uplink offloading communication between a device and an access point of a local area network). In both aforementioned cases, the cellular communication network, in particular an access node or base station thereof, exercises control in establishing and operating corresponding connections and/or transmissions between a device and an access point of a local area network and/or between two devices. Such control typically includes channel access, resource allocation and resource (spectrum) sharing.
For example, a system combination as mentioned above may relate to a LTE-based system utilizing unlicensed spectrum. As mentioned above, applications therein could include e.g. network-controlled D2D or cellular offloading operations, where primary control and configurations, like channel/bearer configurations, are carried out by the LTE network. In other words, higher layer operations and configurations are kept under network control to allow smooth transition between D2D or cellular offloading communication mode and normal cellular (LTE) communication mode, while lower level channel access procedures could be implemented in a non-controlled manner from the serving (LTE) network point of view. This could be realized by having the serving network, like LTE, operating on a licensed spectrum and network-configured D2D or cellular offloading operation taking place on an unlicensed spectrum, e.g. on ISM bands.
However, several problems could arise in such control including channel access, resource allocation and resource (spectrum) sharing, which is mainly due to the differences in usable spectrums and, accordingly, channel access and resource allocation/sharing mechanisms of the two combined network or system types.
While channel access and corresponding resource allocation/sharing control mechanisms are specified in a scheduling-based manner for cellular communication networks (such as LTE), corresponding control mechanisms applicable for local area networks are substantially different in typically being unscheduled or contention-based (also referred to as listen-before-talk (LBT) type mechanisms).
Accordingly, there is a problem in accomplishing channel access and corresponding resource allocation/sharing control mechanisms on an unlicensed spectrum in a manner appropriate for fulfilling the requirements of the corresponding control mechanisms of the higher layer cellular communication network when both such networks or systems are merged. In particular, pure sensing and declaring whether the channel is busy or available for the transmission, as typically used in local are networks, is not enough for such merged systems, e.g. for fulfilling the requirements of a QoS-oriented cellular type (e.g. LTE) system with multiple configured radio bearers and/or logical channels among communicating devices in D2D or cellular offloading connections/or transmissions. Namely, even if a cellular operator decides to offload traffic to an unlicensed band by way of a corresponding D2D or uplink communication, the operator may still want to offer certain QoS levels for the offloaded UE or UEs. Also, even if a cellular operator provides for network-controlled D2D on an unlicensed band in general, the operator may want to offer certain QoS levels for the D2D UEs.
In view thereof, there is a problem in how to take into account specific characteristics (of/from a cellular communication network) in medium access protocol (on an unlicensed band of/from a local area network).
Thus, there is a need to further improve channel access control.